<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="../vue.js"></script>
</head>

<body>
  <div id="app">
    姓:<input type="text" v-model="firstName"><br>
    名:<input type="text" v-model="lastName"><br>
    <p>全名{{fullName}}</p>
    <button @click="upData">更新</button>
  </div>
  <script>
    Vue.config.productionTip = false;

    const vm = new Vue({
      el: "#app",
      data() {
        return {
          firstName: "",
          lastName: ""
        }
      },
      computed: {
        fullName: {
          get() {
            return this.firstName + "-" + this.lastName
          },
          set(value) {
            [this.firstName, this.lastName] = value.split(" ")
          }
        }
      },
      methods: {
        upData() {
          this.fullName = "wang zhongwang"
        }
      }
    })
  </script>
</body>

</html>